| Environmental contamination by heavy metals and metalloids (particularly Arsenic) have occurred at former sites of industrial and agricultural activity. The extent of contamination of surface and ground waters needs to be known before site remediation can take place. In waters, the concentration of such analytes is often below detection. Evaporation of water onto a surface such as x-ray film constitutes a pre-concentration phase allowing the effective lowering of detection limits for dissolved analytes. Instrumentation A PANalytical MiniPal 2 equipped with a 30 kV Rhodium anode tube, 5 different filters and a high-resolution solid state detector was used. Although a Helium purge is available for light element sensitivity enhancement this was not necessary in this case for the heavier elements analysed here. Procedure Synthetic standard solutions were mixed in various ratios and 500 μL of the resulting solution was pipetted onto a dimpled ProleneTM target. The targets were dried under a 100 W light bulb for 12 hours and loaded into the spectrometer. Two excitation conditions were used to acquire the spectra (Table 1). Matrix correction was made by ratioing to a background channel, Bg, with a Region Of Interest (ROI) of 15.300 to 16.000 keV. Table 1. All elements were measured using their Kα line except Ag, Cd, Sn, and U which were measured using their Lα1 lines and Pb where the Lβ1 line was used. | | | As,Bg,Cu,Pb,U,Zn | 30 | 300 | Mo | Air | 100 | | Ag,Al,Cd,Cr,Fe,Ni,Sn | 15 | 40 | Al_thin | Air | 100 | Results Figure 1 and Table 2 show the calibration results for Cr, Zn, As and Pb. There is a good correlation between the supplied concentration values and the measured intensities. 
Figure 1. Calibration graphs for Cr, Zn, As and Pb in synthetic standards. Table 2. Calibration information. Regressions were fitted to 11 synthetic standards evaporated onto X-ray film. | | | Cr | 10 – 201 | 10.94 | 0.9788 | | Zn | 3 – 338 | 5.64 | 0.9983 | | As | 3 – 208 | 11.15 | 0.9807 | | Pb | 4 – 228 | 4.69 | 0.9973 | Repeat analyses of a single sample show excellent repeatability. 
Figure 2. 10 analyses of an evaporated sample. Conclusions These data show that the MiniPal 2 can analyse the selected elements in waters to the required precision. This allows rapid assessment of quite low levels of concentration from industrial and agricultural sites. |